Connie Mulligan, a molecular anthropologist at the University of Florida, disagrees with Harper's conclusions—saying that the existing genetic data do not begin to answer that question.

"Opportunistic timing and the fact that [the voyage and European syphilis outbreak] are so closely tied has provided this interesting historical question: Did he bring it back to the Old World, or was it already present in the Old World?" Mulligan asked.

"We just don't know."

She also notes that at least one theory suggests there is no genetic difference at all between syphilis and its relative ailments.

"Is it just the same disease that has different manifestations in different climates?" she asked.

"That's what I think Harper's data might be showing. ... To me that is very interesting, almost more interesting than the single geographic origin of venereal syphilis.

"In that case, asking where venereal syphilis evolved is the wrong question."

Harper's study was published recently in the journal PLoS Neglected Tropical Diseases.

Yaws, which many scientists believe descended from syphilis, has likely been with humans since their origins in Africa.

"We probably carried it around the world with us," Wells saidm noting that it had likely also infected our ancestors. "Over hundreds of thousands or even millions of years, you slowly start to adjust to each other so that the organism still causes a disease, but it doesn't cause a very bad disease."

"But something happened at some [recent] point that likely allowed it to develop into syphilis, and it took off as a new kind of disease that caused all kinds of problems."

Partial Picture

Wells notes that the genetic study of such diseases can teach us a great deal about the way our own genes have evolved.

"We see clear evidence in our own genome of adaptations to disease," he said. "Recently people have started looking at the genomes of infectious diseases, and we tend to see overlap in those processes [of adaptation]."

The use of genetics to track the origins and movements of disease is a rapidly growing field.